1. Field of the Invention
The present invention relates to a lens and a lens unit for use with a camera or the like, the lens unit being formed by combining a plurality of lenses in an optical-axial direction. More particularly, the invention relates to a lens and a lens unit in which a peripheral edge portion of the lens is bonded and thereby fixed to a lens holder.
2. Description of Related Art
Conventionally, in case of a lens such as a resin optical lens, the lens is bonded with an adhesive to a lens holder and thereby to fixed to the holder. Particularly, in an apparatus used in various environments, the lens is required to be securely bonded. To securely bond a lens to a lens holder, techniques have been developed in which a projecting portion is provided on the periphery of the lens and an adhesive is coated in such a manner as to cover the projecting portion (such techniques are disclosed in Japanese Unexamined Patent Application Publication No. 8-313781, for example).
In this connection, there have also existed lens units formed of multiple optical lenses bonded and fixed to a lens holder at predetermined positions and in predetermined arrangement. By way of general practice, when assembling such a lens unit, a lens to be arranged at an end of the lens unit should be press-held to the lens holder before the adhesive is partially hardened. This makes it difficult to cover the projecting portions with the adhesive in the above-described technique. As such, as is shown in FIG. 5, the arrangement is made such that a peripheral edge portion of an each individual lens is formed extending to the outer circumferential direction so as to be commonly used as a bonding portion and a pressed portion.
Nevertheless, however, a lens unit of the above-described conventional type reduced in diameter has a problem in that a fitting-portion diameter is proportionally reduced and hence the bonding area is proportionally reduced. This leads to potentially insufficiency of adhesion strength. Particularly, for recent mobile apparatuses, requirement for impact resistance is strict, so that further enhancement is demanded in regard to the adhesion strength.